GrahamC

Christmas rush is over, the mad house is now quiet again and I was itching to make a mess of my recently cleaned up lathe. I had run across a reference on the net to something called "lathe alignment buttons". Do a search you will find a few references and photos.

In a nutshell, lathe alignment buttons are simple steel buttons that fit one on on the tailstock dead center point and one on the spindle dead center point. You bring them together and then measure the diameter across the two buttons - the difference from the nominal diameter of the buttons and where in relationship to circumference of the button will tell if your spindle and tailstock are in alignment and if not in what axis or axis'.

As a simple afternoon project I thought I would make a couple and give them a try, I always like to try some of the old ways of doing things and I think these "lathe alignment buttons" have been around a long time. You won't find many references to them on the internet and at that only with reference to gunsmithing.

Now, these things are dead simple to make. There are only two critical dimensions - the nominal outside diameter of each piece and the tapered hole (think center drilled) which fits on the dead center pointy ends. Otherwise anything suitable is just fine.

I started with a piece of 1" leaded steel and turned a sectional to the nominal size - seems the most common nominal size is .900", so that is what I choose. This was a good exercise is aiming for target diameter and hitting it. I managed to get to .9005" - just a wee bit larger so that I could finish it to size later. Sorry, no in progress pictures - simple pictures of just turning metal can be pretty boring.

I laid out each button to be 1/2" in length (notice the dimension 1/2" not .500" - the dimension is not critical). Now I turned the end to 3/4" diameter about 5/16" long so as to leave a portion about 3/16" of the nominal diameter intact. Sharp edges where broken with a file. The end was carefully center drilled and the button parted off to length.

Two buttons where made and the 5C collet chuck mounted up on the lathe. Each button in turn was put in the 3/4" 5c collet and the end faced off and a through hole of 1/8" drilled through. The through hole is not necessary, I only did this so that I would be able to put the button on a piece of stiff wire later on for the "treatment". Sharp edges where broken with a file and the nominal outside diameter again measured and the piece carefully brought to size with a fine file - spot on, both pieces now measure .9000" across the critical diameter of the piece.

"The Treatment" - whenever I make small bits of tooling I more often than not give them "The Treatment". Shiny metal looks OK but to keep oxidation in check and give the pieces a bit of colour I do the following: mount the piece on a bit of stiff wire and start heating with a propane Turbo Torch (I use the BIG burner head). Once the pieces are starting to get hot I dip them in a can of synthetic motor oil which gets the smoke a going. I use synthetic as it is less likely to burn (not all synthetics are pure synthetics, many use a mineral oil base). I don't know if the use of the synthetic helps or not, it is the only type I have ever used for "the treatment" so why change? Continue heating the pieces and quench again after they are quite hot, repeat, and then final heat to red heat and quench once more. Leaded steel does not contain enough carbon to harden nor does something like 1018 CRS. This "treatment" puts a nice blue-black oil/oxide colour/finish on the pieces. It is not as robust as parkerizing or gun bluing but is quite utilitarian. I have never had a piece treated like this take on any rust in the shop whereas many of the pieces I have treated with the common gun bluing solutions ended up rusting in the groves of the threads and in sharp corners despite my best efforts at washing and oiling after treatment.

A quick measure after the treatment shows that the nominal outside critical diameter of both pieces is now .9002".

I tried the buttons on my lathe but jury is still out. I just cannot get them to function as expected; there is too much play. I suspect that the "center drill" bit is off and does not match the dead centers of my lathe very well. I will have to ponder this ponderable for a bit so that I can come to terms with my observations. In any case it was a pleasant way to make spend an afternoon making a mess and giving something different a try. Sorry no picture of the buttons in place on the lathe.

Pictures, pictures, pictures. Well, only two pictures actually. First one shows the two finished buttons in their naked state. The second picture shows the buttons after "the treatment".

Me wonders if you start as though planning to turn between centers. In other words, center drill both ends, actually put it between centers to turn the diameters, face each end (since you can remove and flip end for end between centers), and lastly part it off. Then you can use the faced ends as a reference to get the "middle" ends parallel and flat with a secondary facing operation. Alternatively, make them a little longer and just make two between centers.

Seems like that will yield a touch more accurate part, but I don't know if it will work any better.

GrahamC

Bob, I understand what you are describing and perhaps you are right - it might afford a bit more over all accuracy regarding the relationship between the center drilled hole and the critical outside diameter. If I ever make some more I will give that a try.

However, after much pondering and offering up a dead center to each of the buttons in turn I concluded that the the included angle of the center drilled holes and the included angle of the buttons are different - close but different. They where acting and felt like the holes where a smaller angle than the dead centers.

So, out with the protractor and a light table - not a light table actually, I have one for viewing transparencies but in this case a quick and dirty light table is a sheet of bright white Bristol board (don't know why they call it Bristol board, will have to do a quick Google search on that one) curved up from table top against a small shelf to form a simple reflector and a bright overhead light. Bristol board for those not familiar with the term is a sheet of thin cardboard much like what a cereal box is made from and about a 2 foot by 3 foot rectangle.

Using my ever present and trusty second pair of eyes - an optivisor with 5 diopeter lenses plus a flip down magnifier, I am getting older and my eyes are not quite as sharp unaided as they used to be; I measured up the lathes tail stock 2mt dead center - right on 60 degrees; and the spindle 4mt dead center - right on 60 degrees. Now the center drill - hmm, not 60 degrees. In fact after a bit of fussing to ensure my measurement I discovered the center drill I used for this project is in fact somewhere between 57 and 58 degrees, probably a bit closer to 58 than to 57 but that is a rather moot point when I was in fact expecting it to 60 degrees. The center drill in question has laser etched (I am guessing laser etched) upon it #4 CHINA HSS - maybe 58 degrees makes it a metric center drill ;)

There is nothing else wrong with this center drill, it works very well otherwise, is still quite sharp and in every other aspect is a good center drill. I will remember this one is not 60 degrees and set it aside for other non critical work such as just popping in a center drilled hole as a start to further drilling.

I did get out several other brand name (Hertel - now owned and marketed by Kennametal) center drills and measured them - sure enough, all to a one measured 60 degrees.

So, what is the fix for my lathe alignment buttons - fix the angle of the center drilled holes of course. How? I have an idea and it involves using one of the center drills with the proper 60 degree, a 5C emergency collet and the 5c collet chuck. My only concern is that the new center drill may be pulled off center by the old hole and not be properly centered. I will ponder that some more and I may end up grinding up a small boring tool and "touch up" the present hole to 60 degrees included angle.

GrahamC

However, I did make a choice and proceeded with the repair of these lathe alignment buttons.

I choose to bore the taper rather than rely on that made by a center drill. Reason being that if the tailstock is out of alignment then the hole will be out too.

First task was to set the compound to cut a 60 degree included angle. First photo shows how I did this using the head stock dead center as a reference and indicating off that with a DTI held in the QCTP.

Next step was to modify a 5C emergency collet to hold the alignment buttons while I bored out their taper to the proper angle. The second photo shows the 5C collet after modifications with the wee boring tool I ground up. Interesting how some of the simplest and utilitarian cutting tools work so well. This little wee boring tool I made up some years ago and all I did was touch it up with a stone and put it back to work. It certainly isn't very pretty but it does work well. The third photo shows the 5c collet with button mounted and boring tool in position (this was a staged shot).

The boring went well and easy. A couple of easy and delicate passes to clean up the incorrect taper and to put the taper on center and the fix was done.

And last but not least, the last photo shows the buttons mounted for use on the lathe fitting snugly between the head stock dead center and the tail stock dead center.

A couple of measurements shows just what I already knew - the tail stock center is about .003" high and front to back alignment (across the lathe bed) was spot on. I can see how these will come very handy for quickly aligning the tail stock after I have offset it to turn a taper, it will get it close enough for a lot of uses but not as close using a DTI.

If anyone wishes to try and make something like this, I know think that it is best to bring the taper hole on the backside to final dimensions by boring rather than relying on a center drill to produce the correct tapered hole. Start with the center drill and finish by cleaning up by boring - this will ensure concentricity and the correct angle regardless of how the center drill made the hole.

It has been an interesting little project that had a few interesting twists. Started on a whim to try something different, a bit of tooling I had only seen a brief description of and one picture. So simple in design and use that I couldn't fail.

I got to practice turning to a target diameter. Spent some time in the garage where I do "the treatment" with the doors open for lots of ventilation and enjoyed the days warmer winter weather (0 degrees C).

After having a try at making the newly finished buttons work I discovered much to my dismay that they didn't work as expected. Thinking through the problem, identifying the source of the problem and then coming up with a solution and in the end having made something that worked as it should. Got to use my tools, my hands, and my brain.

And I learned from my failure that it is still a good practice to get only good quality tooling that you can trust. I would have never known that the center drill of Asian origin was not really 60 degrees and for most work it really wouldn't have mattered. It will be good enough for starting a center for further drilling but I won't use any more for anything else.